Self-assembly of extended Schiff base amino acetate skeletons, 2-{[(2Z)-(3-hydroxy-1-methyl-2-butenylidene)]amino}phenylpropionate and 2-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}phenylpropionate skeletons incorporating organotin(IV) moieties: Synthesis, sp

Article abstract of DOI:10.1016/j.jorganchem.2007.06.061

The organotin(IV) compounds, [Ph₃SnL¹H]_n · nCCl₄ (1), [Me₂SnL²(OH₂)] (2), [ⁿBu₂SnL²] (3), [Ph₂SnL²]_n (4), [Ph

Full text of DOI:10.1016/j.jorganchem.2007.06.061

Journal of Organometallic Chemistry 692 (2007) 4849–4862
www.elsevier.com/locate/jorganchem
Self-assembly of extended Schiff base amino acetate skeletons,
2-{[(2Z)-(3-hydroxy-1-methyl-2-butenylidene)]amino}phenylpropionate
and 2-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}phenylpropionate
skeletons incorporating organotin(IV) moieties: Synthesis, spectroscopic
characterization, crystal structures, and in vitro cytotoxic activity
a,
a
b
c
*
´
Tushar S. Basu Baul , Cheerfulman Masharing , Giuseppe Ruisi , Robert Jirasko ,
c
d
e
f,
*
ˇ
Michal Holcapek , Dick de Vos , David Wolstenholme , Anthony Linden
a
Department of Chemistry, North-Eastern Hill University, NEHU Permanent Campus, Umshing, Shillong 793022, India
Dipartimento di Chimica Inorganica e Analitica ‘‘Stanislao Cannizzaro’’ Universita´ di Palermo, Viale delle Scienze, Parco D’Orleans II,
b
Edificio 17, 90128 Palermo, Italy
ˇ
c
University of Purdubice, Faculty of Chemical Technology, Department of Analytical Chemistry, na´m. Cs. legii 565, 53210 Pardubice, Czech Republic
d
Pharmachemie BV, P.O. Box 552, 2003 RN Haarlem, The Netherlands
Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, B3H 4J3, Canada
Institute of Organic Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
e
f
Received 7 June 2007; received in revised form 21 June 2007; accepted 21 June 2007
Available online 4 July 2007
Abstract
The organotin(IV) compounds, [Ph3SnL1H]n Æ nCCl4 (1), [Me2SnL2(OH2)] (2), [nBu2SnL2] (3), [Ph2SnL2]n (4), [Ph3SnL2H]n (5) and
[Ph3SnL3H]n (7) (L1 = 2-{[(2Z)-(3-hydroxy-1-methyl-2-butenylidene)]amino}phenylpropionate and L2ꢀ3 = 2-{[(E)-1-(2-hydroxy-
aryl)alkylidene]amino}phenylpropionate), were synthesized by treating the appropriate organotin(IV) chloride(s) with the potassium salt
of the ligand in a suitable solvent, while [nBu2SnL3(OH2)] (6) was obtained by reacting the acid form of L3 (generated in situ) with
nBu2SnO. These complexes have been characterized by 1H, 13C, 119Sn NMR, ESI-MS, IR and 119mSn Mo¨ssbauer spectroscopic techniques
in combination with elemental analyses. The crystal structures of 1 and 4–7 were determined. The crystal structures of complexes 1, 5 and
7 reveal that the complexes exist as polymeric chains in which the L-bridged Sn-atoms adopt a trans-R3SnO2 trigonal bipyramidal
configuration with R groups in the equatorial positions and the axial locations occupied by a carboxylate oxygen from the carboxylate
ligand and the alcoholic or phenolic oxygen of the next carboxylate ligand in the chain. The carboxylate ligands coordinate in the zwit-
terionic form with the alcoholic/phenolic proton moved to the nearby nitrogen atom. A polymeric zig-zag cis-bridged chain structure is
observed for 4, without considering the weak Snꢁ ꢁ ꢁO interaction, the Sn-atom having a slightly distorted trigonal bipyramidal coordina-
tion geometry with the two O atoms of the tridentate amino propionate ligand in axial positions. On the other hand, the structure of 6
reveals a monomeric molecule in which the Sn-atom has a distorted octahedral coordination geometry involving the tridentate carbox-
ylate ligand, two n-butyl ligands occupying trans-positions and one water ligand. The in vitro cytotoxic activity of triphenyltin(IV) com-
pounds, viz., 1, 5 and 7 against WIDR, M19 MEL, A498, IGROV, H226, MCF7 and EVSA-T human tumor cell lines are also reported.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: Organotin carboxylate; 2-{[(2Z)-(3-hydroxy-1-methyl-2-butenylidene)]amino}phenylpropionate; 2-{[(E)-1-(2-hydroxyaryl)alkylidene]amino}-
phenylpropionate; NMR; ESI-MS; Mo¨ssbauer; Crystal structure; Cytotoxic activity
*
Corresponding authors. Tel.: +91 364 2722626; fax: +91 364 2550486/2721000 (T.S. Basu Baul); tel.: +41 44 635 4228; fax: +41 44 635 6812 (A.
Linden).
E-mail addresses: basubaul@nehu.ac.in, basubaul@hotmail.com (T.S. Basu Baul), alinden@oci.uzh.ch (A. Linden).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.06.061

4850
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 4849–4862
1. Introduction
IR spectra in the range 4000–400 cmꢀ1 were obtained
on a BOMEM DA-8 FT-IR spectrophotometer with sam-
ples investigated as KBr discs. The 1H, 13C and 119Sn
NMR spectra were recorded on a Bruker AMX 400 spec-
trometer and measured at 400.13, 100.62 and
Organotin(IV) carboxylates have been found to show a
variety of interesting molecular architectures [1]. The con-
struction of multidimensional architectures depends on the
combination of several factors including the type of organic
ligands, tin-R groups, tin coordination geometry preferences
and metal-to-ligand molar ratio. In addition, the hydrogen
bonding interactions are important non-coordination and
non-covalent intermolecular forces. Their unique strength
and direction play key roles in the generation of a variety
of supramolecular structures. The self-assembly of organo-
tin(IV) complexed Schiff bases containing the amino acetate
moiety is particularly attractive, since it can be accomplished
in one-pot reactions and allows for easy fine-tuning of struc-
tural and functional features [2–9]. Thus, such Schiff bases
are important building-blocks in the design of extended
structures because of the type and position of the donor
atoms that allow tin atoms to be linked together in diverse
coordination modes (Scheme 1).
Our synthetic efforts are currently aimed towards the
synthesis of supramolecular architectures based on Schiff
bases with an extended amino acetate moiety, which is
slightly bulkier and contains a pro-chiral carbon atom i.e.
2-{[(2Z)-(3-hydroxy-1-methyl-2-butenylidene)]amino}phe-
nylpropionate and 2-{[(E)-1-(2-hydroxyaryl)alkylidene]
amino}phenylpropionate, which were mainly isolated as
potassium salts (Fig. 1). In this paper, we report on the syn-
thesis, spectroscopic and structural characterization of
some new organotin(IV) complexes involving these ligands.
The solid-state structures of a few complexes, e.g.,
[Ph3SnL1H]n Æ nCCl4 (1), [Ph2SnL2H]n (4), [Ph3SnL2H)]n
(5), [nBu2SnL3H(OH2)] (6) and [Ph3SnL3H]n (7) have been
determined using single crystal X-ray crystallography in
order to bestow deeper insight into their coordination
geometry and supramolecular structure. The tin coordina-
tion of these complexes in solution has been deduced from
119Sn NMR data in non-coordinating solvent, while the
cleavage of the most labile bond in each molecule has been
studied using ESI mass spectroscopy.
1
149.18 MHz. The H, 13C and 119Sn chemical shifts were
referred to Me4Si set at 0.00 ppm, CDCl3 set at
77.0 ppm and Me4Sn set at 0.00 ppm, respectively. The
Mo¨ssbauer spectra were recorded with a conventional
spectrometer operating in the transmission mode. The
source was Ca119SnO3 (Ritverc GmbH, St. Petersburg,
Russia; 10 mCi), moving at room temperature with con-
stant acceleration in a triangular waveform. The driving
system was from Halder (Seehausen, Germany), and the
NaI (Tl) detector from Harshaw (De Meern, The Nether-
lands). The multichannel analyser and the related elec-
tronics were from Takes (Bergamo, Italy). The solid
absorber samples, containing ca. 0.5 mg 119Sn cmꢀ2, were
held at 77.3 K in a MNC 200 liquid-nitrogen cryostat
(AERE, Harwell, UK). The velocity calibration was made
using a 57Co Mo¨ssbauer source (Ritverc GmbH, St.
Petersburg, Russia, 10 mCi), and an iron foil as absorber.
The isomer shifts are relative to room temperature
Ca119SnO3. Positive-ion and negative-ion electrospray
ionization (ESI) mass spectra were measured on an ion
trap analyzer Esquire 3000 (Bruker Daltonics, Bremen,
Germany) in the range m/z 50–2000. The complexes were
dissolved in acetonitrile or methanol and analyzed by
direct infusion at a flow rate of 5 ll/min. The selected pre-
cursor ions were further analyzed by MS/MS analyses
under the following conditions: an isolation width of
m/z = 8 for ions containing one tin atom and m/z = 12
for ions containing more tin atoms, an ion source
temperature of 300 ꢁC, a tuning parameter of compound
stability 100%, a flow rate and pressure of nitrogen of
4 l/min and 10 psi, respectively. The software IsoPro 3.0
(freeware, http://members.aol.com/msmssoft/) was used
for the theoretical calculation of relative isotopic
abundances.
2.3. Synthesis of ligands
2. Experimental
A typical procedure is described below.
2.1. Materials
2.3.1. Synthesis of potassium 2-{[(E)-1-(2-hydroxyphenyl)
methylidene]amino}phenylpropionate (L2HK)
Ph3SnCl (Fluka AG), Ph2SnCl2, nBu2SnCl2 (Merck),
Me2SnCl2 (Aldrich), L-phenylalanine, 2-hydroxybenzalde-
hyde, acetylacetone (Sisco) and 2-hydroxyacetophenone
(Aldrich) were used without further purification. The sol-
vents used in the reactions were of AR grade and were
dried using standard procedures. Benzene was distilled
from sodium benzophenone ketyl.
A cold aqueous solution (3 ml) of KOH (0.83 g,
14.8 mmol) was mixed with a cold aqueous solution
(10 ml) containing L-phenylalanine (2.44 g, 14.8 mmol)
and was held at 15–20 ꢁC in an ice bath with continuous
stirring. A methanolic solution (15 ml) of 2-hydroxybenz-
aldehyde (1.81 g, 14.8 mmol) was added drop-wise. A
deep-yellow colour developed almost immediately and
stirring was continued for 1 h, followed by 5 h stirring
at room temperature. The volatiles were removed care-
fully; the yellow mass was stirred in diethylether and fil-
tered. The residue was dissolved in a minimum amount
2.2. Physical measurements
Carbon, hydrogen and nitrogen analyses were per-
formed with a Perkin Elmer 2400 series II instrument.

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 4849–4862
4851
Scheme 1. An overview showing the coordination behaviour of Schiff bases with amino acids towards organotin(IV).
of anhydrous methanol and filtered. The filtrate was pre-
cipitated with diethylether which afforded the crude
product. Repeated precipitations from a methanol–dieth-
ylether mixture yielded L2HK in 85% (3.86 g) yield.
M.p.: 178–179 ꢁC. Anal. Calc. for C16H14NKO3: C,
62.52; H 4.59; N; 4.55. Found: C, 63.01; H, 5.23; N,
4.25%. IR (cmꢀ1): 1628 m(OCO)asym, 1605 m(C@N),
1275 m(Ph(C–O)).

4852
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 4849–4862
K+
O
K+
K+
-O
O-
3'
8
9
-O
1
8
6
12
13
9
2
4
3
3
4
N
1
O
1
O
7
4
10 11
8
9
3
5
2
2
12
13
14
7
HO
N
N
6
5
6
7
10
11
5'
10
OH
14
3'
5
OH
(L1HK)
(L2HK)
(L3HK)
Fig. 1. The generic structures of the ligands, their abbreviations and numbering scheme.
2.3.2. Potassium 2-{[(2Z)-(3-hydroxy-1-methyl-2-
119Sn NMR (CDCl3): ꢀ99.3 ppm. 119Sn Mo¨ssbauer:
d = 1.21, D = 3.14, C = 0.80 mm sꢀ1, q = 2.59. ESI-MS:
MW = Mmono = 597 = L1HSnPh3. Positive-ion MS: m/z
948 [Mmono+SnPh3]+; m/z 636 [Mmono+K]+; m/z 620
[Mmono+Na]+, 100%; m/z 351 [SnPh3]+. Negative-ion
MS: m/z 843 [Mmono+L1H]ꢀ, 100%; m/z 439
[ClSnPh3+Cl+H2O]ꢀ; m/z 246 [L1H]ꢀ; m/z 202
[L1HꢀCO2]ꢀ.
butenylidene)]amino}phenylpropionate (L1HK)
The same procedure was followed as for L2HK, except
that the reaction mixture was refluxed. Recrystallization
from a methanol–diethylether mixture gave a yellow pre-
cipitate in 80% yield. M.p.: 200–201 ꢁC. Anal. Calc. for
C14H16NKO3: C, 58.94; H 5.65; N; 4.90. Found: C,
59.36; H, 5.71; N, 4.90%. IR (cmꢀ1): 1613 m(OCO)asym
1613 m(C@N), 1314 m(Ph(C–O)).
,
2.4.2. Synthesis of [Me2SnL2(OH2)] (2)
2.3.3. Potassium 2-{[(E)-1-(2-hydroxyphenyl)
ethylidene]amino}phenylpropionate (L3HK)
A solution of Me2SnCl2 (0.35 g, 1.59 mmol) in CCl4
(5 ml) was added drop-wise to a suspension of L2HK
(0.49 g, 1.59 mmol) in CCl4 (20 ml) under stirring condi-
tions at room temperature. The stirring was continued
for 5 h. The reaction mixture was filtered; the filtrate was
reduced to one-fourth of its initial solvent volume and then
precipitated with hexane to give a yellow coloured product.
The crude product was washed thoroughly with hexane,
dried in vacuo and re-crystallized from CCl4/hexane (2:1
v/v) which afforded a yellow crystalline product of 2 in
63% (0.49 g) yield. m.p.: 82–84 ꢁC. Anal. Calc. for
C18H21NO4Sn: C, 49.75; H, 4.98; N, 3.22. Found: C,
The same procedure was followed as for L2HK and the
work-up of the reaction mixture yielded a yellow pasty
mass which could not be isolated in powder form. So, the
potassium salt was generated in situ prior to the reaction
with the organotin reactant.
2.4. Synthesis of the organotin(IV) complexes
2.4.1. Synthesis of [Ph3SnL1H]n Æ nCCl4 (1)
A warm solution of Ph3SnCl (0.5 g, 1.30 mmol) in anhy-
drous methanol (ca. 10 ml) was added drop-wise to a warm
solution of L1HK (0.37 g, 1.30 mmol) in anhydrous meth-
anol (ca. 20 ml) under stirring conditions. The reaction
mixture was refluxed for 5 h, then filtered and the filtrate
was then evaporated to dryness and the residue was dried
in vacuo. The dried mass was washed thoroughly with hex-
ane, dried in vacuo, extracted in carbon tetrachloride (ca.
20 ml) and filtered while hot. The filtrate was left to evap-
orate slowly at room temperature to afford light-yellow
crystals of 1 in 77% (0.59 g) yield. M.p.: 138–139 ꢁC. Anal.
Calc. for C33H31Cl4NO3Sn: C, 52.85; H, 4.16; N, 1.87.
Found: C, 52.64; H, 4.25; N, 2.17%. IR (cmꢀ1): 1657
m(OCO)asym, 1600 m(C@N), 1310 m(Ph(CO)). 1H NMR
(CDCl3): ligand skeleton: 10.70 (brs, 1H, OH), 7.01 (m,
5H, H-8, H-9 and H-10), 4.66 (s, 1H, H-4), 4.09 (q, 1H,
H-2), 2.70 and 3.0 (dd, 2H, H-6), 1.74 and 1.40 (s, 6H,
H-30 and H-50); Sn–Ph skeleton: 7.62 (m, 6H, H-2*), 7.29
(m, 9H, H-3* and H-4*), ppm. 13C NMR (CDCl3): ligand
skeleton: 193.8 (C-1), 174.7 (C-3), 162.2 (C-5), 137.2 (C-
7), 129.3 (C-8), 128.3 (C-9), 126.5 (C-10), 95.6 (C-4), 59.2
(C-2), 39.3 (C-6), 28.3 and 18.9 (C-30 and C-50); Sn–Ph
skeleton [nJ(13C–119Sn, Hz)]: 140.0 (C-1*) [600], 136.8
(C-2*) [54], 129.6 (C-4*) [16], 128.7 (C-3*) [60], ppm.
50.01; H, 4.80; N, 3.33%. IR (cmꢀ1): 1669 m(OCO)asym
,
1
1613 m(C@N), 1302 m(Ph(CO)). H NMR (CDCl3): ligand
skeleton: 7.58 (s, 1H, H-3), 7.41 (t, 1H, H-7), 7.27 (m,
4H, H-12 and H-13), 7.13 (m, 1H, H-14), 6.85 (dd, 1H,
H-9), 6.76 (dd, 1H, H-6), 6.68 (t, 1H, H-8), 4.20 (q, 1H,
H-2), 3.49 and 3.12 (dd, 2H, H-10); Sn-Me skeleton: 0.63
and 0.65 (s, 6H), ppm. 13C NMR (CDCl3): ligand skeleton:
172.5 (C-1 and C-3), 168.9 (C-5), 137.7 (C-7), 135.2 (C-9),
135.0 (C-11), 130.2 (C-12), 128.9 (C-13), 127.5 (C-14),
122.5 (C-6), 117.2 (C-8), 116.7 (C-4), 69.8 (C-2), 41.9 (C-
10); Sn–Me skeleton: 0.22 and 0.55, ppm. 119Sn NMR
(CDCl3): ꢀ157.5 ppm. 119Sn Mo¨ssbauer: d = 1.25,
D = 3.69, C = 0.95 mm sꢀ1, q = 2.95. ESI-MS: MW =
M
mono = 417. Positive-ion MS: m/z 873 [2*Mmono+K]+;
m/z 857 [2*Mmono+Na]+; m/z 456 [Mmono+K]+; m/z 440
[Mmono+Na]+, 100%; m/z 418 [Mmono+H]+. Negative-ion
MS: m/z 416 [Mmono-H]ꢀ, 100%.
2.4.3. Synthesis of [nBu2SnL2] (3)
This compound was prepared in the same manner as
described for 2 by using nBu2SnCl2 (0.44 g, 1.48 mmol)
and L2HK (0.40 g, 1.49 mmol). After work-up, the crude
product was re-crystallized from chloroform which upon

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 4849–4862
4853
slow evaporation afforded a yellow crystalline product of 3
in 70% (0.57 g) yield. M.p.: 123–124 ꢁC. Anal. Calc. for
C24H31NO3Sn: C, 57.63; H, 6.24; N, 2.80. Found: C,
(brs, 1H, OH), 7.80 (s, 1H, H-3), 7.18 (m, 5H, H-12, H-
13 and H-14), 6.95 (m, 2H, H-7 and H-9), 6.78 (dd, 1H,
H-6), 6.59 (t, 1H and H-8), 4.06 (q, 1H and H-2), 3.18
and 3.01 (dd, 2H, H-10); Sn–Ph skeleton: 7.56 (m, 6H,
H-2*), 7.28 (m, 9H, H-3* and H-4*), ppm. 13C NMR
(CDCl3): ligand skeleton: 176.5 (C-1), 166.2 (C-3), 161.1
(C-5), 137.2 (C-11), 132.5 (C-7), 131.6 (C-9), 129.3 (C-
12), 128.3 (C-13), 126.6 (C-14), 118.7 (C-4), 118.4 (C-6),
117.0 (C-8), 73.0 (C-2), 40.6 (C-10); Sn–Ph skeleton
[nJ(13C–119Sn, Hz)]: 137.7 (C-1*) [610], 136.8 (C-2*) [50],
130.3 (C-4*) [20], 129.0 (C-3*) [60], ppm. 119Sn-NMR
(CDCl3): ꢀ99.7 ppm. 119Sn Mo¨ssbauer: d = 1.21,
57.50; H, 6.50; N, 2.80%. IR (cmꢀ1): 1668 m(OCO)asym
,
1
1616 m(C@N), 1296 m(Ph(CO)). H NMR (CDCl3): ligand
skeleton: 7.45 (s, 1H, H-3), 7.39 (t, 1H, H-7), 7.24 (m,
4H, H-12 and H-13), 7.12 (m, 1H, H-14), 6.75 (m, 2H,
H-6 and H-9), 6.63 (t, 1H, H-8), 4.16 (q, 1H, H-2), 3.54
and 3.04 (dd, 2H, H-10); Sn–nBu skeleton: 1.69–1.57 (m,
4H, H-1*), 1.51–1.21 (m, 8H, H-2* and H-3*), 0.94 and
0.79 (t, 6H, H-4*), ppm. 13C NMR (CDCl3): ligand skele-
ton: 173.0 (C-1), 172.4 (C-3), 169.5 (C-5), 137.6 (C-7),
135.3 (C-9 and C-11), 130.2 (C-12), 128.9 (C-13), 127.5
(C-14), 122.4 (C-6), 117.0 (C-8), 116.8 (C-4), 69.9 (C-2),
41.9 (C-10); Sn–nBu skeleton: 27.0 and 26.8 (C-2*), 26.6
and 26.4 (C-3*), 21.7 and 21.6 (C-1*), 13.5 and 13.4 (C-
4*), ppm. 119Sn NMR (CDCl3): ꢀ198.3 ppm. 119Sn Mo¨ss-
bauer: d = 1.19, D = 2.70, C = 0.84 mm sꢀ1, q = 2.27.
ESI-MS: MW = Mmono = 501. Positive-ion MS: m/z 1025
[2*Mmono+Na]+, 100%; m/z 540 [Mmono+K]+; m/z 524
[Mmono+Na]+; m/z 502 [Mmono+H]+. Negative-ion MS:
m/z 500 [Mmono-H]ꢀ, 100%.
D = 3.04, C
mono = 619 = L2HSnPh3. Positive-ion MS: m/z 992
= 0.75 mm sꢀ1, q = 2.51. ESI-MS: MW =
M
[Mmono+NaꢀH+SnPh3]+; m/z 970 [Mmono+SnPh3]+,
100%; m/z 658 [Mmono+K]+; m/z 642 [Mmono+Na]+; m/z
351 [SnPh3]+. Negative-ion MS: m/z 887 [Mmono+ligand]ꢀ,
100%; m/z 618 [Mmono-H]ꢀ; m/z 574 [MmonoꢀHꢀCO2]ꢀ;
m/z 439 [ClSnPh3+Cl+H2O]ꢀ; m/z 351 [SnPh3]ꢀ; m/z 224
[ligandꢀCO2]ꢀ; m/z 197 [ligandꢀCO2-27]ꢀ.
2.4.6. Synthesis of [nBu2SnL3(OH2)] (6)
n
A mixture of Bu2SnO (0.4 g, 1.60 mmol), l-phenylala-
2.4.4. Synthesis of [Ph2SnL2]n (4)
nine (0.26 g, 1.60 mmol) and 2-hydroxyacetophenone
(0.22 g, 1.60 mmol) were refluxed in ethanol (30 ml) for
8 h using a Dean and Stark apparatus. The clear yellowish
green solution was evaporated using a rotary evaporator.
Then anhydrous toluene (30 ml) was added to the syrupy
mass and refluxed for 6 h using a Dean and Stark setup.
The reaction mixture was filtered while hot and the filtrate
was evaporated to give a yellow mass, which upon recrystal-
lization from a toluene/hexane (1:1) mixture furnished a
pure product of 6 in 66% (0.56 g) yield. M.p.: 94–95 ꢁC.
Anal. Calc. for C25H35NO4Sn: C, 56.43; H, 6.63; N, 2.63.
Found: C, 56.50; H, 6.70; N, 2.70%. IR (cmꢀ1): 1641
m(OCO)asym, 1601 m(C@N), 1311 m(Ph(CO)). 1H NMR
(CDCl3): ligand skeleton: 7.34 (m, 2H, H-7 and H-9), 7.24
(m, 5H, H-12, H-13 and H-14), 6.89 (m, 1H, H-6), 6.72 (t,
1H, H-8), 4.68 (q, 1H, H-2), 3.51 and 3.08 (dd, 2H, H-10),
2.18 (s, 3H, H-30); Sn–nBu skeleton: 1.80–1.67 (m, 4H, H-
1*), 1.51–1.11 (m, 8H, H-2* and H-3*), 0.95 and 0.74 (t,
6H, H-4*), ppm. 13C NMR (CDCl3): ligand skeleton:
179.8 (C-1), 173.4 (C-3), 166.9 (C-5), 135.5 (C-7), 135.4
(C-9), 130.1 (C-11), 129.8 (C-12), 129.0 (C-13), 127.4 (C-
14), 123.8 (C-6), 120.8 (C-4), 117.6 (C-8), 65.1 (C-2), 41.0
(C-10), 22.1 (C-30); Sn–nBu skeleton: 27.2 and 26.8 (C-2*),
26.6 and 26.3 (C-3*), 20.2 and 18.1 (C-1*), 13.5 and 13.3
(C-4*), ppm. 119Sn NMR (CDCl3): ꢀ208.8 ppm. 119Sn
An identical method to that for 2 was followed using
Ph2SnCl2 and L2HK. Yellow crystals of compound 4 were
obtained from ethanol in 58% yield. M.p.: 168–170 ꢁC.
Anal. Calc. for C28H23NO3Sn: C, 62.27; H, 4.29; N, 2.59.
Found: C, 62.31; H, 4.05; N, 2.67%. IR (cmꢀ1): 1679
m(OCO)asym, 1614 m(C@N), 1304 m(Ph(CO)). 1H NMR
(CDCl3): ligand skeleton: 8.00 (t, 1H, H-7), 6.85 (dd, 1H,
H-9), 7.22 (s, 1H, H-3), 7.12 (m, 5H, H-12, H-13 and H-
14), 6.92 (dd, 1H, H-6), 6.68 (t, 1H, H-8), 4.18 (q, 1H,
H-2), 3.50 and 2.70 (dd, 2H, H-10); Sn-Ph skeleton: 7.48
(m, 4H, H-2*), 7.38 (m, 6H, H-3* and H-4*), ppm. 13C-
NMR (CDCl3): ligand skeleton: 173.0 (C-1), 172.1 (C-3),
169.3 (C-5), 135.4 (C-7), 135.0 (C-11), 130.0 (C-9), 129.0
(C-12), 128.9 (C-13), 127.4 (C-14), 122.7 (C-6), 117.7 (C-
8), 116.8 (C-4), 70.5 (C-2), 41.5 (C-10); Sn-Ph skeleton:
138.0 and 137.9 (C-1*), 136.6 and 136.4 (C-2*), 130.8 and
130.7 (C-4*), 128.9 (C-3*), ppm. 119Sn NMR (CDCl3):
ꢀ341.8 ppm. 119Sn Mo¨ssbauer: d = 1.15, D = 3.57,
C
= 0.81 mm sꢀ1, q = 3.10. ESI-MS: MW = Mmono
=
541. Positive-ion MS: m/z 1121 [2*Mmono+K]+; m/z 1105
[2*Mmono+Na]+; m/z 580 [Mmono+K]+, 100%; m/z 564
[Mmono+Na]+; m/z 542 [Mmono+H]+. Negative-ion MS:
m/z 540 [Mmono-H]ꢀ, 100%.
2.4.5. Synthesis of [Ph3SnL2H]n (5)
Mo¨ssbauer: d = 1.34, D = 3.64,
C
= 0.87 mm sꢀ1
,
An identical method to that for 1 was followed using
Ph3SnCl and L2HK, except that the reaction was con-
ducted in anhydrous benzene for 5 h. Yellow crystals of
compound 5 were obtained from ethanol in 70% yield.
M.p.: 157–159 ꢁC. Anal. Calc. for C34H29NO3Sn: C,
66.05; H, 4.72; N, 2.26. Found: C, 66.10; H, 4.70; N,
2.37%. IR (cmꢀ1): 1662 m(OCO)asym, 1609 m(C@N), 1313
m(Ph(CO)). 1H NMR (CDCl3): ligand skeleton: 12.50
q = 2.71. ESI-MS: MW = Mmono = 515. Positive-ion MS:
m/z 1053 [2*Mmono+Na]+, 100%; m/z 554 [Mmono+K]+;
m/z 538 [Mmono+Na]+; m/z 516 [Mmono+H]+. Negative-
ion MS: m/z 514 [MmonoꢀH]ꢀ, 100%.
2.4.7. Synthesis of [Ph3SnL3H]n (7)
An anhydrous methanol solution (2 ml) of KOH (0.09 g,
1.60 mmol) was added to a round bottom flask containing

4854
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 4849–4862
˚
l-phenylalanine (0.27 g, 1.63 mmol) in 2 ml of methanol
and the reaction mixture was stirred until a clear solution
was obtained. To this, a methanol solution (3 ml) of 2-
hydroxyacetophenone (0.22 g, 1.61 mmol) was added
drop-wise and refluxed for 2 h. Then, a solution of Ph3SnCl
(0.62 g, 1.61 mmol) in anhydrous methanol (5 ml) was
added and the reaction mixture was refluxed for an addi-
tional 5 h. The volatiles were removed and the residue
was washed thoroughly with petroleum ether (60–80 ꢁC)
and dried in vacuo. The dried residue was extracted into
warm chloroform (25 ml) and filtered. The filtrate was con-
centrated, precipitated with petroleum ether (60–80 ꢁC), fil-
tered and the yellow coloured precipitate was dried in
vacuo. The crude product was then re-crystallized from a
chloroform–ethanol (1:1 v/v) mixture which afforded a
lemon yellow microcrystalline product of 7 in 60%
(0.53 g) yield. M.p.: 158–159 ꢁC. Anal. Calc. for
C35H31NO3Sn: C, 66.43; H, 4.94; N, 2.21. Found: C,
radiation (k = 0.71073 A) and an Oxford Cryosystems
Cryostream 700 cooler. Data reductions were performed
with HKL DENZO and SCALEPACK [11]. The intensities were
corrected for Lorentz and polarization effects, and empirical
absorption corrections based on the multi-scan method [12]
were applied. Equivalent reflections were merged, other
than the Friedel pairs for1 and 7. The data collection and
refinement parameters are given in Table 1, and views of
the molecules are shown in Figs. 2–6. The structures were
solved by direct-methods using SIR92 [13] for 1, 4, 5 and 7,
and SHELXS97 [14] for 6, and the non-hydrogen atoms were
refined anistropically.
Compounds 1, 4, 5 and 7 exist as polymeric chains with
the carboxylate ligands bridging between the Sn-atoms and
in each case the asymmetric unit contains just one of the
chemical repeat units of the polymer. In 1, the asymmetric
unit also contains one molecule of CCl4. One of the phenyl
ligands is disordered. Two sets of positions were defined for
all atoms of the disordered phenyl ring, except for the ipso
C-atom and the site occupation factor of the major confor-
mation refined to 0.673(4). Neighbouring atoms within and
between each conformation of the disordered phenyl ring
were restrained to have similar atomic displacement
parameters.
The carboxylate ligand in 5 is disordered from the car-
boxylate group through to and including the benzyl group.
The disorder includes one of the carboxylate O-atoms,
O(2), but not C(1). Two sets of overlapping positions were
defined for the disordered atoms and the site occupation
factor of the major conformation refined to 0.678(6). Sim-
ilarity restraints were applied to the chemically equivalent
bond lengths and angles involving all disordered atoms,
while neighbouring atoms within and between each confor-
mation were restrained to have similar atomic displacement
parameters. Pesudo-isotropic restraints were also applied
to the disordered position of the carboxylate carbonyl
O-atom.
In 6, there are two symmetry-independent monomeric
molecules in the asymmetric unit. The terminal ethyl group
of one butyl ligand of one of the symmetry-independent
molecules is disordered over two conformations. Two sets
of overlapping positions were defined for the disordered
atoms and the site occupation factor of the major confor-
mation refined to 0.566(8). Similarity restraints were
applied to the chemically equivalent bond lengths and
angles involving all disordered C-atoms, while neighbour-
ing atoms within and between each conformation of the
disordered group were restrained to have similar atomic
displacement parameters. The water ligand H-atoms were
placed in the positions indicated by a difference electron
density map and their positions were allowed to refine
together with individual isotropic displacement parame-
66.80; H, 5.01; N, 2.30%. IR (cmꢀ1): 1658 m(OCO)asym
,
1
1605 m(C@N), 1314 m(Ph(CO)). H NMR (CDCl3): ligand
skeleton: 14.8 (brs, 1H, OH), 7.21 (m, 5H, H-12, H-13
and H-14), 6.99 (m, 2H, H-7 and H-9), 6.76 (dd, 1H, H-
6), 6.54 (t, 1H, H-8), 4.46 (q, 1H, H-2), 3.32 and 3.01
(dd, 2H, H-10), 1.68 (s, 3H, H-30); Sn-Ph skeleton: 7.61
(m, 6H, H-2*), 7.31 (m, 9H, H-3* and H-4*), ppm. 13C
NMR (CDCl3): ligand skeleton: 177.0 (C-1), 171.5 (C-3),
163.0 (C-5), 137.3 (C-11), 131.9 (C-7), 129.5 (C-9), 128.2
(C-12), 127.8 (C-13), 126.4 (C-14), 119.6 (C-4), 118.6 (C-
6), 116.7 (C-8), 64.4 (C-2), 40.8 (C-10), 14.3 (C-30); Sn-Ph
skeleton [nJ(13C–119Sn, Hz)]: 137.7 (C-1*) [620], 136.9 (C-
2*) [50], 129.9 (C-4*) [16], 128.7 (C-3*) [60], ppm. 119Sn
NMR (CDCl3): ꢀ98.3 ppm. 119Sn Mo¨ssbauer: d = 1.22,
D = 3.10,
C
= 0.81 mm sꢀ1
,
q = 2.54.
ESI-MS:
MW = Mmono = 633 = L3HSnPh3. Positive-ion MS: m/z
1006 [Mmono+NaꢀH+SnPh3]+; m/z 984 [Mmono+SnPh3]+;
m/z 672 [Mmono+K]+; m/z 656 [Mmono+Na]+, 100%; m/z
634 [Mmono+H]+; m/z 351 [SnPh3]+. Negative-ion MS:
m/z
915
[Mmono+ligand]ꢀ,
100%;
m/z
439
[ClSnPh3+Cl+H2O]ꢀ; m/z 351 [SnPh3]ꢀ; m/z 238
[ligandꢀCO2]ꢀ.
For the H and 13C NMR assignments, refer to Fig. 1
1
for the numbering scheme of the ligand skeleton, while
for the Sn–R skeleton, the numbering is as shown below:
3*
2*
4*
CH
3*
CH
2*
CH
1*
CH
1*
Sn,
Sn , 4*
2
3
2
2
2.5. X-ray crystallography
Crystals of compounds 1, 4–7 suitable for an X-ray crys-
tal-structure determination were obtained from carbon tet-
rachloride (1), ethanol (4 and 5), toluene/hexene (6) or
acetone (7) solutions of the respective compounds. All mea-
surements were made at 160 K on a Nonius KappaCCD
diffractometer [10] with graphite-monochromated Mo Ka
˚
ters, while lightly restraining the O–H distances to 0.84 A.
For 7, the ammonium H-atom was placed in the posi-
tion indicated by a difference electron density map and its
position was allowed to refine together with an isotropic
displacement parameter. All other H atoms in all structures

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 4849–4862
4855
Table 1
Crystallographic data and structure refinement parameters for compounds 1 and 4–7
1
4
5
6
7
Empirical formula
Formula weight
Crystal size (mm)
Crystal color, habit
Crystal system
C32H31NO3SnÆCCl4
750.02
C28H23NO3Sn
540.09
0.15 · 0.17 · 0.25
Pale yellow, prism
Monoclinic
P21/c
11.5921(2)
9.2157(2)
21.6622(4)
90
96.7398(9)
90
C34H29NO3Sn
618.21
0.05 · 0.07 · 0.12
Yellow, prism
Monoclinic
P21/c
11.0911(2)
12.8357(3)
20.0734(4)
90
105.180(1)
90
C25H35NO4Sn
532.15
0.15 · 0.25 · 0.28
Colorless, prism
Triclinic
C35H31NO3Sn
632.23
0.13 · 0.20 · 0.33
Colorless, prism
Orthorhombic
P212121
11.0077(2)
17.3960(2)
17.6395(2)
90
0.12 · 0.17 · 0.32
Yellow, prism
Orthorhombic
P212121
11.2346(1)
12.5781(2)
20.8002(3)
90
ꢀ
Space group
P1
˚
a (A)
9.9886(2)
12.5048(2)
20.2658(3)
81.703(1)
89.952(1)
79.9294(8)
2465.45(7)
4
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
90
90
90
90
3
˚
V (A )
3377.79(8)
4
1.475
2298.17(8)
4
1.561
2758.0(1)
4
1.489
2939.27(7)
4
1.429
Z
Dx (g cmꢀ3
)
1.434
1.065
l (mmꢀ1
)
1.105
1.141
0.962
0.904
Transmission factors (min, max)
2hmax (ꢁ)
0.791; 0.895
60
65005
9852; 0.065
8315
427
102
0.036
0.082
1.08
0.745; 0.848
56
44041
5481; 0.061
4618
299
0.884; 0.956
52
46415
5417; 0.078
4516
435
236
0.043
0.084
1.25
0.676; 0.858
60
55207
14222; 0.053
11556
601
36
0.038
0.096
1.07
0.831; 0.900
60
51297
8605; 0.058
7772
367
Reflections measured
Independent reflections; Rint
Reflections with I > 2r(I)
Number of parameters
Number of restraints
R(F) [I > 2r(I) reflections]
WR(F2) (all data)
0
0
0.034
0.084
1.14
0.032
0.067
1.07
GOF(F2)
Secondary extinction coefficient
–
0.0013(3)
1.46; ꢀ0.90
0.0025(5)
0.61; ꢀ0.65
–
0.0015(2)
1.28; ꢀ0.85
ꢀ3
˚
Dqmax, min (e A
)
1.30; ꢀ1.03
2.38; ꢀ1.51
Fig. 2. Three repeats of the crystallographically and chemically unique unit in the polymeric [Ph3SnL1H]n chain structure of 1 (50% probability ellipsoids;
1
2
1
2
1
2
1
2
only one of the conformations of the disordered phenyl ring is shown; symmetry operators: 0 ꢀ x; ꢀ þ y; ꢀ z; 00 ꢀ x; þ y; ꢀ z). The hydrogen atoms
have been omitted for clarity.
were placed in geometrically calculated positions and
refined using a riding model where each H atom was
assigned a fixed isotropic displacement parameter with a
value equal to 1.2 Ueq of its parent C atom (1.5 Ueq for
the methyl groups). The refinement of each structure was
carried out on F2 using full-matrix least-squares proce-
dures, which minimized the function Rw(Fo ꢀFc )2. Cor-
rections for secondary extinction were applied for 4, 5
and 7. Refinement of the absolute structure parameter
[15] for 1 and 7 yielded a value of ꢀ0.04(2) in each case,
which confidently confirms that the refined coordinates
represent the true enantiomorph. All calculations were per-
formed using the SHELXL97 program [16].
2.6. Biological tests
2
2
The in vitro cytotoxicity test of compounds 1, 5 and 7
was performed using the SRB test for the estimation of
cell viability. The cell lines WIDR (colon cancer), M19
MEL (melanoma), A498 (renal cancer), IGROV (ovarian

4856
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 4849–4862
Fig. 3. Three repeats of the crystallographically and chemically unique unit in the polymeric [Ph3SnL2H]n chain structure of 5 (50% probability ellipsoids;
0
1
2
1
2
only one of the conformations of the disordered carboxylate ligand is shown; symmetry operators: 2 ꢀ x; þ y; 1 12 ꢀ z; 002 ꢀ x; ꢀ þ y; 1 21 ꢀ z). The
hydrogen atoms have been omitted for clarity.
Fig. 4. Three repeats 0of the crystallographically and chemically unique unit in the polymeric [Ph3SnL3H]n chain structure of 7 (50% probability ellipsoids;
1
symmetry operators: 2 ꢀ x; 12 þ y; 21 ꢀ z; 002 ꢀ x; ꢀ þ y; 12 ꢀ z). The hydrogen atoms have been omitted for clarity.
2
cancer) and H226 (non-small cell lung cancer) belong to
the currently used anticancer screening panel of the
National Cancer Institute, USA [17]. The MCF7 (breast
cancer) cell line is estrogen receptor (ER)+/progesterone
receptor (PgR)+ and the cell line EVSA-T (breast cancer)
is (ER)ꢀ/(Pgr)ꢀ. Prior to the experiments, a mycoplasma
test was carried out on all cell lines and found to be neg-
ative. All cell lines were maintained in a continuous loga-
rithmic culture in RPMI 1640 medium with Hepes and
phenol red. The medium was supplemented with 10%
FCS, penicillin 100 lg/ml and streptomycin 100 lg/ml.
The cells were mildly trypsinized for passage and for
use in the experiments. RPMI and FCS were obtained
from Life technologies (Paisley, Scotland). SRB, DMSO,
Penicillin and streptomycin were obtained from Sigma
(St. Louis MO, USA), TCA and acetic acid from Baker
BV (Deventer, NL) and PBS from NPBI BV (Emmer-
Compascuum, NL).

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 4849–4862
4857
construction of concentration–response curves and the
determination of ID50 values by use of Deltasoft 3
software.
The variability of the in vitro cytotoxicity test depends
on the cell lines used and the serum applied. With the same
batch of cell lines and the same batch of serum the inter-
experimental CV (coefficient of variation) is 1–11%
depending on the cell line and the intra-experimental CV
is 2–4%. These values may be higher with other batches
of cell lines and/or serum.
The in vitro cytotoxicity experiments were carried out by
Ms. P.F. van Cuijk in the Laboratory of Translational
Pharmacology, Department of Medical Oncology, Eras-
mus Medical Center, Rotterdam, The Netherlands, under
the supervision of Dr. E. A. C. Wiemer and Prof. Dr. G.
Stoter.
3. Results and discussion
3.1. Synthetic aspects
Fig. 5. Three repeats of the crystallographically and chemically unique
unit in the polymeric [Ph2SnL2]n chain structure of 4 showing the cis-
bridged Ph2SnL2 chain (50% probability ellipsoids; symmetry operators:
The organotin(IV) complexes (1–5) were prepared by
reacting the potassium salts of the ligands (L1ꢀ2HK;
Fig. 1) with the appropriate organotin(IV) halide(s) in 1:1
molar ratios in appropriate solvents (see Section 2.4). On
the other hand, the 2-{[(E)-1-(2-hydroxyphenyl)ethyli-
dene]amino}phenylpropionic acid (L3HH0) or its potas-
sium salt (L3HK) could not be isolated as powder.
However, both L3HH0 and L3HK frameworks can be gen-
erated in situ and can be used for the reactions with appro-
priate organotin(IV) oxide or halide(s), respectively, which
yielded rest of the organotin(IV) complexes (6–7). The
details of their synthesis and characterization data are pre-
sented in Section 2.4. The complexes were obtained in good
yield and purity. They are stable in air and soluble in all
common organic solvents.
1
0 ꢀ x; 12 þ y; 1 21 ꢀ z; 00 ꢀ x; ꢀ þ y; 1 21 ꢀ z). s. The hydrogen atoms have been
2
omitted for clarity.
The test compounds 1, 5 and 7 and reference com-
pounds were dissolved to a concentration of 250000 ng/
ml in full medium by 20-fold dilution of a stock solution,
which contained 1 mg of compounds 1, 5 and 7/200 ll.
All the three compounds were dissolved in DMSO. Cyto-
toxicity was estimated by the microculture sulforhodamine
B (SRB) test [18].
2.6.1. Experimental protocol and cytotoxicity tests
The experiment was started on day 0. On day 0, 150 ll
of trypsinized tumor cells (1500–2000 cells/well) were pla-
ted in 96-well flat-bottomed micro-titer plates (falcon
3072, BD). The plates were pre-incubated for 48 h at
37 ꢁC, 5.5% CO2 to allow the cells to adhere. On day 2, a
3-fold dilution sequence of 10 steps was made in full med-
ium, starting with the 250000 ng/ml stock solution. Every
dilution was used in quadruplicate by adding 50 ll to a col-
umn of four wells. This results in a highest concentration of
62500 ng/ml being present in column 12. Column 2 was
used for the blank. To column 1, PBS was added to dimin-
ish interfering evaporation. On day 7, washing the plate
twice with PBS terminated the incubation. Subsequently,
the cells were fixed with 10% trichloroacetic acid in PBS
and placed at 4 ꢁC for an hour. After three washings with
tap water, the cells were stained for at least 15 min with
0.4% SRB dissolved in 1% acetic acid. After staining, the
cells were washed with 1% acetic acid to remove the
unbound stain. The plates were air-dried and the bound
stain was dissolved in 150 ll (10 mM) Tris-base. The absor-
bance was read at 540 nm using an automated microplate
reader (Labsystems Multiskan MS). Data were used for
3.2. Crystal structures
The molecular structures of compounds 1, and 4–7 are
shown in Figs. 2–6 (see Scheme 2 for line diagrams), while
selected geometric parameters are collected in Tables 2–5.
The crystal structures of complexes 1, 5 and 7 are very
similar and exhibit the same structural motif of a polymeric
chain where a single carboxylate ligand bridges adjacent
R3Sn centres via its carboxylate and oxide O-atoms, as
illustrated in Figs. 2–4. The asymmetric unit in each struc-
ture contains one of the chemical repeat units of the poly-
meric Sn-compound, while 1 includes additionally one
molecule of CCl4. The primary coordination sphere of
the Sn-atom is trigonal bipyramidal with the phenyl ligands
in the equatorial plane and the axial positions being occu-
pied by one O-atom from the carboxylate group of one
ligand and the oxide O-atom (formerly the hydroxy group)
of the next carboxylate ligand in the chain. In each struc-
ture, the chains propagate in the crystallographic [010]
direction. A polymeric structure with a similar mode of

4858
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 4849–4862
Fig. 6. (a) The molecular structure of one of the disordered conformations of one of the two symmetry-independent molecules (molecule A) of
[nBu2SnL3(OH2)] (6) (50% probability ellipsoids). (b) The molecular packing of [nBu2SnL3 (OH2)] (6) showing the intermolecular hydrogen bonding (thin
lines).
coordination and geometry about the Sn-atom was
observed in [Ph3Sn{2-OHC6H4C(H) = NCH2COO}n] [4].
The second O-atom of the carboxylate group is not
involved in the primary coordination sphere of the Sn-
atom, but coordinates very weakly to the Sn-atom via a
the N-atom of the C@N group is protonated, thus leading
to a zwitterionic ligand. This N–H group forms an intra-
molecular hydrogen bond with the oxide O-atom. It is
worth mentioning that the crystals of compounds 1 and 7
are enantiomerically pure (S-configuration of the zwitter-
ionic carboxylate ligand) and their absolute configuration
has been determined independently by the diffraction
experiment. On the other hand, the carboxylate ligand in
5 is disordered from the carboxylate group through to
the benzyl group (see Section 2.5). This disorder results
from random coordination of either an R-configured or
S-configured ligand at each Sn-atom. This comes about
because both enantiomers of the racemic ligand apparently
have similar spatial requirements. One of the phenyl
˚
long Snꢁ ꢁ ꢁO(2) interaction of about 3.53 A (see Table 2,
although this is still within the sum of the van der Waals
˚
radii of the respective atoms (ca. 3.6 A). There does not
appear to be any major distortion of the trigonal bipyrami-
dal Sn-coordination geometry as a result of the Snꢁ ꢁ ꢁO(2)
contact. Similar additional weak Snꢁ ꢁ ꢁO coordination
was also observed in the structures of related polymeric
[Ph3SnLH]n derivatives [8]. The formal hydroxy group
has lost its H-atom, so it is negatively charged. Instead

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 4849–4862
4859
Table 4
Selected bond lengths (A) and angles (ꢁ) for compound 6
˚
Molecule A
Molecule B
Sn(1)–O(1)
Sn(1)–O(3)
Sn(1)–O(4)
Sn(1)–N(1)
Sn(1)–C(10)
Sn(1)–C(11)
2.152(2)
2.201(2)
2.390(2)
2.259(2)
2.126(3)
2.122(3)
Sn(2)–O(5)
Sn(2)–O(7)
Sn(2)–O(8)
Sn(2)–N(2)
Sn(2)–C(40)
Sn(2)–C(41)
2.158(2)
2.193(2)
2.420(2)
2.258(2)
2.121(3)
2.121(3)
O(1)–Sn(1)–C(10)
O(1)–Sn(1)–C(11)
O(1)–Sn(1)–O(3)
O(1)–Sn(1)–O(4)
O(1)–Sn(1)–N(1)
O(3)–Sn(1)–C(10)
O(3)–Sn(1)–C(11)
O(3)–Sn(1)–O(4)
O(3)–Sn(1)–N(1)
O(4)–Sn(1)–C(10)
O(4)–Sn(1)–C(11)
O(4)–Sn(1)–N(1)
N(1)–Sn(1)–C(10)
N(1)–Sn(1)–C(11)
C(10)–Sn(1)–C(11)
95.60(9)
100.6(1)
152.04(7)
77.98(7)
73.47(7)
89.96(9)
83.97(9)
129.96(7)
78.59(7)
82.71(9)
83.6(1)
O(5)–Sn(2)–C(40)
O(5)–Sn(2)–C(41)
O(5)–Sn(2)–O(7)
O(5)–Sn(2)–O(8)
O(5)–Sn(2)–N(2)
O(7)–Sn(2)–C(40)
O(7)–Sn(2)–C(41)
O(7)–Sn(2)–O(8)
O(7)–Sn(2)–N(2)
O(8)–Sn(2)–C(40)
O(8)–Sn(2)–C(41)
O(8)–Sn(2)–N(2)
N(2)–Sn(2)–C(40)
N(2)–Sn(2)–C(41)
C(40)–Sn(2)–C(41)
95.07(9)
100.70(9)
152.74(6)
78.38(7)
73.74(7)
90.15(9)
84.39(9)
128.88(7)
79.00(7)
81.54(9)
83.39(9)
152.12(7)
100.60(9)
101.76(9)
155.5(1)
Scheme 2. Structure of the complexes 1, 4–7.
151.45(8)
99.92(9)
101.5(1)
156.1(1)
Table 2
a
˚
Selected bond lengths (A) and angles (ꢁ) for compounds 1, 5 and 7
1
5
7
Sn–O(1)
Sn–O(30)
Sn–O(2)
Sn–C(17)
Sn–C(23)
Sn–C(29)
2.152(2)
2.323(2)
3.507(2)
2.129(3)
2.131(3)
2.126(3)
2.191(3)
2.251(3)
ca. 3.55
2.138(4)
2.118(4)
2.131(3)
2.182(2)
2.284(2)
3.539(2)
2.129(3)
2.123(3)
2.132(2)
Table 5
a
˚
Hydrogen bonding geometry (A, ꢁ) for 6
D–Hꢁ ꢁ ꢁA
D–H
Hꢁ ꢁ ꢁA
Dꢁ ꢁ ꢁA
D–Hꢁ ꢁ ꢁA
O(4)–H(41)ꢁ ꢁ ꢁO(60)
O(4)–H(42)ꢁ ꢁ ꢁO(7)
O(8)–H(81)ꢁ ꢁ ꢁO(2)
O(8)–H(82)ꢁ ꢁ ꢁO(300)
a
0.82(2)
0.80(2)
0.81(2)
0.82(2)
1.87(2)
1.94(2)
1.91(2)
1.94(2)
2.689(3)
2.741(3)
2.719(3)
2.752(3)
178(4)
174(4)
174(4)
176(4)
C(17)–Sn–C(23)
C(17)–Sn–C(29)
C(23)–Sn–C(29)
O(1)–Sn–O(30)
a
123.4(1)
114.5(1)
121.4(1)
175.89(8)
123.2(2)
117.3(2)
118.9(2)
169.13(9)
120.5(1)
117.3(1)
121.3(1)
169.64(6)
Primed atoms refer to the molecule in the following symmetry related
positions: 1 þ x; y; z; 00 ꢀ 1 þ x; y; z.
0
Primed atoms refer to atoms from the next symmetrically-related
ligand in the polymeric chain (symmetry code for 1: ꢀx, ꢀ 2 þ y, 12 ꢀ z; for
1
ligands in 1 is disordered over two orientations which differ
by a rotation of 55.8(6)ꢁ about the Sn–C bond.
5: 2 ꢀ x, 2 þ y, 112 ꢀ z; for 7: 2 ꢀ x, 2 þ y, 2 ꢀ z).
1
1
1
In the crystal structure of 4, the Sn-complex units are
linked into a polymeric zig-zag cis-bridged chain by a
Sn(1)–O(2)0 (symmetry operation of primed atom ¼ ꢀx;
Table 3
a
˚
1
2
1
˚
Selected bond lengths (A) and angles (ꢁ) for compound 4
þ y; 1 2 ꢀ z) interaction of 2.402(2) A (Table 3) involving
Sn(1)–O(1)
Sn(1)–O(3)
Sn(1)–O(20)
Sn(1)–O(10)
Sn(1)–N(1)
Sn(1)–C(10)
Sn(1)–C(11)
2.200(2)
2.135(2)
2.402(2)
3.313(2)
2.237(2)
2.119(3)
2.130(3)
the Sn-atom and the exocyclic carboxylate carbonyl O-
atom of the tridentate ligand of a neighboring Sn-complex
unit (Fig. 5). The chain propagates in the crystallographic
[010] direction. The coordination geometry of the Sn-atom
is best described as that of a rather distorted octahedron in
which the Sn(1)–O(2)0 bond is almost trans to one of the
phenyl groups. This contrasts with the trigonal bipyrami-
dal coordination geometry observed in the related diphe-
nyltin(IV) amino acetate [6].
In contrast to the polymeric structures encountered for
complexes 1, 4, 5 and 7, the crystal structure of 6 reveals
a monomeric molecule in which the Sn-atom has a
distorted octahedral coordination geometry involving the
tridentate carboxylate ligand, two n-butyl ligands occupy-
ing trans-positions (C(10)–Sn(1)–C(11) = 156.1(1)ꢁ) and
one water ligand (Fig. 6a and Table 4). An essentially
similar coordination geometry was found for an aqua
O(1)–Sn(1)–C(10)
O(1)–Sn(1)–C(11)
O(1)–Sn(1)–O(3)
O(1)–Sn(1)–N(1)
O(3)–Sn(1)–C(10)
O(3)–Sn(1)–C(11)
O(3)–Sn(1)–N(1)
N(1)–Sn(1)–C(10)
N(1)–Sn(1)–C(11)
C(10)–Sn(1)–C(11)
a
96.3(1)
91.9(1)
154.39(8)
73.28(8)
89.2(1)
90.9(1)
81.16(8)
98.9(1)
100.0(1)
160.9(1)
Primed atoms refer to atoms from the next symmetrically-related
ligand in the polymeric chain (symmetry code: ꢀx, 2 þ y, 112 ꢀ z).
1

4860
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 4849–4862
divinyltin(IV) amino acetate analogue [2]. The occupation
of a Sn coordination site by the water ligand in 6 presum-
ably prevents the formation of a polymeric structure by
blocking the possibility for coordination of the carboxylate
carbonyl O atom of another carboxylate ligand to the Sn-
atom, as occurred in 4. In all other respects, the coordina-
tion behaviour of the tridentate carboxylate ligand in 4 and
6 is the same. It should be noted that the Sn-atom in com-
plex 6 was found to be five-coordinate in solution (see Sec-
tion 3.3).
There are two symmetry-independent molecules in the
asymmetric unit in the crystal structure of 6. Aside from
variations in the conformations of the n-butyl ligands,
the two independent molecules have very similar geome-
tries (Table 4). The terminal ethyl group of one n-butyl
ligand of one of the symmetry-independent molecules is
disordered over two conformations. The water ligand in
molecule A forms intermolecular hydrogen bonds with
the phenoxy O-atom of molecule B and the carboxylate
carbonyl O-atom of a different molecule B (Table 5). These
interactions links the molecules into extended
ꢁ ꢁ ꢁAꢁ ꢁ ꢁBꢁ ꢁ ꢁAꢁ ꢁ ꢁBꢁ ꢁ ꢁ chains, in which molecule A acts twice
as a donor and molecule B acts twice as an acceptor. The
chains run parallel to the [100] direction and can be
described by a graph set motif [19] of C22(8). Within these
chains, the water ligand in molecule B interacts in a similar
fashion with the carboxylate carbonyl O-atom of the origi-
nal molecule A and the phenoxy O-atom of a different mol-
ecule A, thereby forming a second strand of interactions
within the ꢁ ꢁ ꢁAꢁ ꢁ ꢁBꢁ ꢁ ꢁAꢁ ꢁ ꢁBꢁ ꢁ ꢁ chains, in which molecule
B now acts twice as a donor and molecule A acts twice
as an acceptor (see Fig. 6b).
nyltin(IV) derivatives [Ph3Sn{O2CC6H4(N = N(C6H3-4-
OH-5-CHO))-o}OH2] [22], [Ph3Sn{2-OC6H4C(H) =
NCH2CO2}]n [4] and [Ph3Sn{O2C(CH2)2N = CH(C6H4-2-
OH)}]n [8] which are all characterized by a trans-O2 trigo-
nal bipyramidal geometry. These results are in agreement
with the structures determined by X-ray crystallography
(see Section 3.2) after ignoring the long Snꢁ ꢁ ꢁO contact,
which has no significant influence on the trigonal bipyrami-
dal geometry.
Concerning the diorganotin(IV) derivatives, the crystal-
lographic data show that the amino acetate moiety acts as a
dianionic O,N,O tridentate ligand, the tin atom expanding
the coordination number to six through carboxylate bridg-
ing (complex 4) or coordination by a water molecule (com-
plex 6). The D values observed for these derivatives are
consistent with distorted trans-R2Sn octahedral structures.
Simplified point-charge calculations, based on the assump-
tion that the electric field gradient on tin nucleus is domi-
nated by the highly covalent Sn–C bonds [23], give C–
Sn–C bond angle estimates of 157ꢁ and 147ꢁ for complexes
4 and 6, respectively, which fit reasonably well with the
experimental crystallographic values (Tables 3 and 4).
The quadrupole splitting value for complex 2, [Me2Sn-
L2(OH2)], D = 3.69 mm sꢀ1, is typical of distorted trans-
R2Sn octahedral structures and fully comparable with that
of complex 6, and that of the analogous aqua di-n-
butyltin(IV) amino acetate [nBu2Sn{2-OC6H4C(CH3) =
NCH2CO2}(OH2)]2, which has also been characterized
crystallographically (see Ref. [24] for the Mo¨ssbauer data
and Ref. [6] for the crystal structure). On this basis, and
in view of the similarity of the ligands, it can be inferred
that complex 2 assumes the same structure as complex 6.
Complex 3, [nBu2SnL2], is characterized by a quadru-
pole splitting value of 2.70 mm sꢀ1 which strongly suggests
3.3. Spectroscopy
n
a cis-R2Sn trigonal bypiramidal structure with Bu groups
The solid-state IR spectra displayed a strong sharp band
in the range 1640–1680 cmꢀ1 for diorganotin(IV) com-
plexes (2–4 and 6) and at around 1660 cmꢀ1 for triorgano-
tin(IV) complexes (1, 5 and 7) which has been assigned to
the carboxylate antisymmetric [masym(OCO)] stretching
vibration, in accord with our earlier reports [2,4,5,8]. The
assignment of the symmetric [msym(OCO)] stretching vibra-
tion band could not be made owing to the complex pattern
of the spectra.
In order to obtain further structural conclusions in the
solid-state, the Mo¨ssbauer spectra of the complexes have
been recorded and are listed in Section 2.4. The spectra
show a characteristic doublet absorption with narrow line
width, C, indicating the occurrence of unique tin coordina-
tion sites in all compounds. The isomer shift (d) values
found (1.15–1.34 mm sꢀ1) are typical of quadrivalent
organotin derivatives [20]. The triphenyltin(IV) complexes
(1, 5 and 7) exhibit very similar 119Sn Mo¨ssbauer spectra
characterized by D values of ꢂ3.10 mm sꢀ1, which are char-
acteristic of trigonal bipyramidal structures with phenyl
groups in equatorial positions and axial electronegative
ligands [20,21]. Similar D values were found for the triphe-
and a nitrogen atom in the equatorial plane and oxygen
atoms in axial positions. Polymerization through carboxyl-
ate bridges, as observed in complex 4, can be ruled out.
Thus, 119Sn Mo¨ssbauer results provide a reliable indicator
in the structural characterization of the organotin(IV)
complexes, especially in the absence of crystallographic
data.
1
The H and 13C NMR signals were assigned by the use
of homonuclear correlated spectroscopy (COSY), hetero-
nuclear single-quantum correlation (HSQC) and heteronu-
clear multiple-bond connectivities (HMBC) experiments.
1
The H and 13C chemical shift assignment (Section 2.4)
of the organotin moiety is straightforward from the multi-
1
plicity patterns and resonance intensities. The H NMR
integration values were completely consistent with the for-
mulation of the products. The 13C NMR spectra of the
ligand and Sn–R skeletons displayed the expected carbon
signals in all cases. It should be noted that the diorgano-
1
tin(IV) complexes 2–4 and 6, all displayed two sets of H
and 13C NMR signals from the Sn–R groups indicating
that the two R groups experience different environments
on the NMR time scale.

T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 4849–4862
4861
The solution-state structures of complexes 1–7 were
derived from 119Sn NMR chemical shifts, which are sum-
marized in Section 2.4. The triphenyltin(IV) complexes
(1, 5 and 7) in CDCl3 exhibit a single sharp resonance at
around ꢀ99.0 ppm, suggesting that the Sn-atoms in the
complexes have the same four-coordinate environment
[4,8,25,26]. These results demonstrate that the polymeric
structure with five-coordinate tin atoms found in the solid
state is lost upon dissolution (see Section 3.2 for the crystal
structure discussion). On the other hand, the chemical shift
data for complexes 2, 3 and 6 in CDCl3 suggest that in non-
coordinating solvents all species are monomeric, with pen-
tacoordinated tin atoms bound to two oxygen atoms, one
nitrogen atom and two alkyl groups, since all chemical
shifts appear in the typical range for a trigonal bipyramidal
geometry [27]. This is further supported by our recent work
on analogous dialkyltin(IV) carboxylates of cognate
ligands [6,24]. The corresponding solid-state Mo¨ssbauer
data of complexes 2 and 6 indicate a trans-R2Sn octahedral
geometry (because of an additional H2O ligand) while com-
plex 3 shows a trigonal bipyramidal geometry where the
interaction due to the H2O ligand is absent. This is in
agreement with the results obtained from the X-ray crystal
structure determination of the complex 6 (vide supra),
which indicated that in the solid state the Sn-atom has a
distorted octahedral coordination geometry. Thus, the
119Sn NMR result specifies that the six-coordinate Sn-atom
in the solid state structures of complexes 2 and 6 (as
revealed by the crystal structures and the Mo¨ssbauer
spectra, vide supra) is lost upon dissolution giving rise to
a five-coordinate Sn-atom in solution. The diphenyltin(IV)
complex 4 displayed a 119Sn chemical shift at ꢀ341 ppm in
solution, which closely matches the shifts reported for
diphenyltin(IV) amino acetate [2,24], which has five-coordi-
nate Sn-atoms in solution. This shift testifies that the poly-
meric structure of 4, revealed in the crystal structure, is also
not retained in solution.
The ESI mass spectra of the complexes 1–7 were
recorded in order to confirm the molecular weights (from
first-order mass spectra), to verify the structural features
(from tandem mass spectra; MSn) and to examine the
cleavage of the most labile bond in each molecule [28–
32]. The most common ions observed in the first-order
positive-ion mass spectra are sodium or potassium ion
adducts and in some cases also protonated molecules,
which are used for the verification of molecular weights
of monomeric units (Mmono). Moreover, the adducts of
monomeric units with SnPh3 are observed for triphenyl-
tin(IV) compounds (1, 5 and 7) and dimeric ions for diorg-
anotin(IV) compounds 2–4 and 6. The formation of similar
adducts is known in the ESI mass spectra of complex
organotin(IV) compounds [22,33]. On the other hand, the
most common ions observed in the first-order negative-
ion mass spectra are anionic adducts [Mmono+ligand]ꢀ,
except for compounds 2–4 and 6, which have no signal in
the negative-ion mode in acetonitrile solution. The mass
spectra do not provide the information on the polymeric
structures of compounds 1, 4, 5 and 7 as identified by X-
ray crystallography, which can probably be explained by
easy fragmentation even under the softest ionization condi-
tions, but the masses of the monomeric units and the struc-
tures of particular ligands are confirmed based on the
characteristic ions described in Section 2.4.
3.4. In vitro cytotoxicity
The results of the in vitro cytotoxicity tests performed
with some triphenyltin(IV) compounds, (1, 5 and 7) are
summarized in Table 6 and the screening results are com-
pared with the results from other related triphenyltin(IV)
Table 6
In vitro ID50 values (ng/ml) of test compounds 1, 5 and 7 along with some reported triphenyltin(IV) compounds against some standard drugs used as cell
viability tests in seven human tumour cell linesa
Test compoundb
Cell lines
A498
EVSA-T
H226
IGROV
M19 MEL
MCF-7
WIDR
[Ph3SnL1H]nÆnCCl4 (1)
[Ph3SnL2H]n (5)
[Ph3SnL3H]n (7)
DOX
CDDP
5-FU
MTX
ETO
TAX
Ph3SnR1 [34]
Ph3SnR2 [34]
Ph3SnR3 [34]
CDDP
105
120
113
90
2253
143
37
1314
<3.2
42
81
100
96
105
115
108
199
3269
340
2287
3934
<3.2
39
101
105
106
60
169
297
7
580
<3.2
19
102
130
112
16
558
442
23
505
<3.2
42
111
115
110
10
699
750
18
2594
<3.2
17
106
110
109
11
967
225
<3.2
150
<3.2
17
8
422
475
5
317
<3.2
<3
<3
<2
422
8
65
<2
2253
90
61
<2
3269
199
18
<2
169
60
51
<2
558
16
16
2.9
699
10
19
<2
967
11
DOX
a
Abbreviation: DOX = doxorubicin, CDDP = cisplatin, 5-FU = 5-fluorouracil, MTX = methotrexate, ETO = etoposide and TAX = paclitaxel; for
reported triphenyltin(IV) compounds, R is a carboxylate residue where R1 = -terebate, R2 = -steroidcarboxylate, R3 = -benzocrowncarboxylate.
b
Standard drug reference values are cited immediately after the test compounds under identical conditions.

4862
T.S. Basu Baul et al. / Journal of Organometallic Chemistry 692 (2007) 4849–4862
[5] T.S. Basu Baul, S. Dutta, C. Masharing, E. Rivarola, U. Englert,
Heteroatom. Chem. 14 (2003) 149.
[6] T.S. Basu Baul, C. Masharing, R. Willem, M. Biesemans, M.
compounds with respect to the standard drugs that are in
current clinical use as antitumour agents. Recently, we have
reported in vitro cytotoxic results on a diorganotin(IV) com-
pound {[nBu2Sn(2-OHC6H4C(CH3) = N(CH2)2COO)]2O}2
where the ligand is a Schiff base derived from b-alanine [8].
On the basis of this study, the present investigation was
designed to investigate organotin(IV) compounds with
improved in vitro antitumor activity. Indeed an improved
activity was observed for the triphenyltin(IV) compounds
of the present investigation (see Table 6). The activity was
found to be better than that of CDDP (cisplatin). Interest-
ingly, all the three triphenyltin(IV) compounds of the pres-
ent investigation show comparable cytotoxic activity across
a panel of cell lines studied. This encouraging cytotoxic
effect is predictive of in vivo antitumour activity. Com-
pounds 1, 5 and 7 may be suitable candidates for modifica-
tion in order to improve dissolution properties which may
influence cytotoxicity. Although the triphenyltin(IV) com-
pounds in the present investigation possess quite high
in vitro cytotoxicity, it should be noted that the triphenyl-
tin(IV) -terebate, -steroidcarboxylate and -benzocrown-
carboxylate are even more cytotoxic in vitro (see Table 6)
[34]. Different active organotin(IV) compound may still
show slight variation in in vitro cytotoxicity due to different
kinetic and mechanistic behaviour [8]. In conclusion, the
present study reports new structures with improved
in vitro anti-tumor activity which is of added value in deter-
mining the structure–activity relationship in the area of
organotin(IV) chemistry with possible future clinical
application.
´
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Struct. Chem. 18 (2007) 231.
[10] R. Hooft, KappaCCD Collect Software, Nonius BV, Delft, The
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Inorganic Chemistry, Plenum Press, New York, 1984, pp. 527–575
(Chapter 16).
[24] T.S. Basu Baul, S. Dutta, E. Rivarola, M. Scopelliti, S. Choudhuri,
Appl. Organomet. Chem. 15 (2001) 947.
4. Supplementary material
CCDC 648364, 648365, 648366, 648367 and 648368 con-
tain the supplementary crystallographic data for 1, 4, 5, 6
and 7, respectively. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre
via http://www.ccdc.cam.ac.uk/data_request/cif.
´
´
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[25] J. Holecˇek, M. Nadvornık, K. Handlir, A. Lycka, J. Organomet.
Chem. 241 (1983) 177.
[26] R. Willem, I. Verbruggen, M. Gielen, M. Biesemans, B. Mahieu,
T.S. Basu Baul, E.R.T. Tiekink, Organometallics 17 (1998) 5758.
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[27] J. Holecˇek, M. Nadvornık, K. Handlir, A. Lycka, J. Organomet.
Acknowledgements
Chem. 315 (1986) 299.
[28] C.L. Gatlin, F. Turecˇek, in: R.B. Cole (Ed.), Electrospray Ionization
of Inorganic and Organometallic Complexes in Electrospray Ioniza-
tion Mass Spectrometry: Fundamentals, Instrumentation and Appli-
cations, Wiley, New York, 1997, pp. 527–570.
The financial support of the Department of Science &
Technology, New Delhi, India (Grant No. SR/S1/IC-03/
2005, TSBB) and the Ministry of Education, Youth and
Sports of the Czech Republic (Grant Project No.
MSM0021627502, R.J. and M.H.) are gratefully acknowl-
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˚
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[29] A. Ruzˇicˇka, L. Dostal, R. Jambor, V. Buchta, J. Brus, I. Cısarˇova,
M. Holcˇapek, J. Holecˇek, Appl. Organomet. Chem. 16 (2002) 315.
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